Abstract
Lactate dehydrogenase is a tetrameric enzyme, generally composed of one or two kinds of subunits each encoded in a separate gene. Most vertebrates synthesize five major isozymic forms of lactate dehydrogenase, but the salmonid fish, particularly trout, synthesize many more. The numerous lactate dehydrogenase isozymes of trout can be selectively removed from tissue homogenates by suitably prepared antisera to specific lactate dehydrogenase subunits of fish. Electrophoretic resolution of such antisera-treated homogenates then permits an identification of each isozyme and a determination of its subunit composition and probable genetic basis. Such data indicate that trout are tetraploid organisms and have duplicate and slightly different loci for two and perhaps three of the lactate dehydrogenase loci found in other fish. The evolutionary relationships among the lactate dehydrogenase loci can also be assessed by these immunochemical data.